Reductions in vehicle fuel consumption and emissions have been pursued by attempting to employ fuel cells. In addition, solid oxide fuel cells (SOFC) have been proposed to meet an increasing demand for on-board electricity. Vehicles equipped with a SOFC auxiliary power unit could allow operation of electrical accessories without drawing down batteries, even when the main propulsion system is not operating.
A fuel cell is an energy conversion device that generates electricity and heat by electrochemically combining a gaseous fuel, such as hydrogen, carbon monoxide, or a hydrocarbon, and an oxidant, such as air or oxygen, across an ion-conducting electrolyte. The fuel cell converts chemical energy into electrical energy. A fuel cell generally consists of two electrodes positioned on opposite sides of an electrolyte. The oxidant passes over the oxygen electrode (cathode) while the fuel passes over the fuel electrode (anode). The primary outputs of fuel cells are electricity, heat, and water.
A SOFC is constructed entirely of solid-state materials, utilizing an ion conductive ceramic oxide as the electrolyte. A conventional electrochemical cell in a SOFC is comprised of an anode and a cathode with an electrolyte disposed therebetween. In a typical SOFC, a fuel flows to the anode where it is oxidized by oxygen ions from the electrolyte, producing electrons that are released to the external circuit, and mostly water and carbon dioxide are removed in the fuel flow stream. At the cathode, the oxidant accepts electrons from the external circuit to form oxygen ions. The oxygen ions migrate across the electrolyte to the anode. The flow of electrons through the external circuit provides for consumable or storable electrical power. However, each individual electrochemical cell generates a relatively small voltage. Higher voltages are attained by electrically connecting a plurality of electrochemical cells in series to form a stack.
The SOFC stack and other major system components operate at temperatures of about 600xc2x0 C. up to about 1,000xc2x0 C. At these temperatures, the components are glowing orange to white hot requiring radiation shielding and insulation to reduce energy loss and protect the surrounding vehicle surfaces. The thermal energy emitted from the system must be controlled for warm-up and cool-down periods, as well as during operation. Containing and controlling the thermal energy from the SOFC system is critical to the operation of the system. Conventional methods of containing and controlling the thermal energy from the SOFC system require the use of expensive insulation and heat pipes, which would be bulkier and heavier.
The drawbacks and disadvantages of the prior art are overcome by the thermal management for a vehicle mounted solid oxide fuel cell system.
A method of thermal management of a fuel cell transportation vehicle is disclosed. The method comprises directing a first air having a temperature less than a chamber temperature towards at least one surface of the hot box. At least a portion of the air is passed through at least one chamber wall to an interior of the chamber, reducing the surface temperature.
A fuel cell transportation vehicle thermal management system is disclosed. The system comprises a chamber comprising insulation and a fuel cell stack in fluid communication with a reformer, a system enclosure disposed around the chamber, and a process air system in fluid communication with at least one surface of the chamber.
A method of thermal management of a fuel cell transportation vehicle is disclosed. The method comprises directing a first air having a temperature less than a chamber temperature towards at least one surface of the chamber. The surface temperature is reduced from a temperature of up to about 200xc2x0 C. to a temperature of about 90xc2x0 C. or less.
The above described and other features are exemplified by the following figures and detailed description.